U.S. and Mexico Cooperating To Control
Water-Hyacinth Infestation

Agricultural Research
Service scientists are collaborating with Mexican researchers in an effort
to curb the spread of the aquatic weed water-hyacinth--Eichhornia
crassipes-- in Mexicos dikes, reservoirs and canals. The researchers
have introduced two weevils and a moth as biological control agents that have
proven to be successful in reducing water-hyacinth densities in the United
States.

The two weevils--Neochetina bruchi and Neochetina
eichhorniae--were first released in the United States in the early 1970s by
Ted Center and other ARS scientists. Center, of ARS
Invasive
Plant Research Laboratory in Ft. Lauderdale, Fla., currently leads
ARS involvement with this project in Mexico. Since then both weevils have
been shown to suppress water-hyacinth mat expansion by causing the development
of smaller, less intertwined mats which eventually led to significant declines
in infestation levels.

This success and others like it in far-flung corners of the
globe like South Africa, Malaysia and Egypt prompted Mexican researchers to
introduce the weevils in infested irrigation systems in the state of Sinaloa,
on the Pacific coast of Mexico. In western Sinaloa, water-hyacinth infestation
has caused obstruction of canals, clogged ditches and other severe problems in
60 irrigation districts.

Researchers have recently found that the weevils have
dramatically reduced water-hyacinth mats throughout Sinaloas irrigation
districts in two to three years, compared to three to 10 years in other areas.
At a number of locations, biomass coverage was reduced from 90-100 percent to
less than 5 percent. Adult females will chew a hole in the stem of a leaf to
deposit a single egg. A single adult female weevil will lay more than 400 eggs
during her lifetime.

The scientists also found that some weevils were infected with a
microsporidian-like organism. These parasitic spores reduce the weevils
ability to lay eggs. Studies have shown that only 14 percent of infected
females lay eggs compared to 100 percent of healthy females. This finding
allowed researchers to eliminate infected breeding lines, which helped optimize
the weevils performance once released.